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Microfluidic fabrication of hollow protein microcapsules for controlled release.

The microencapsulation of bioactive compounds has been widely applied by food processors in order to improve the stability of these compounds and control their release after they are consumed.

Controlling the release rate of bioactive compounds in our gastrointestinal tracts is crucial to providing an effective dose of the compounds and avoiding side effects. Controlling the release properties of the core material is also of great importance.

A novel approach to encapsulation involves droplet-based microfluidics, capable of producing sophisticated microcapsules in one step.

Microcapsules with a variety of desirable structures can be designed and fabricated on microfluidic chips, including non-spherical particles, porous microcapsules, dendritic microcapsules, cross-linked protein capsules and biological microgels. Two immiscible phases used in droplet-based systems are the continuous phase (the medium in which droplets flow) and the dispersed phase (the droplet phase).

Food materials, due to their physical and chemical complexity, have had limited success with microfluidic processes. So, scientists at the University of Illinois set out to develop a microfluidic technique for fabricating hollow microcapsules with tunable release rates, using the food-grade protein zein. Theirs is a novel approach to tuning the release properties of microcapsules made of food proteins. This approach could expand the application of food materials as effective controlled-release media.

The researchers produced hollow zein microcapsules in a T-junction microfluidic chip through internal phase separation driven by the self-assembly of zein. The dispersed phase was composed of three amounts--2%, 4% and 6%--of zein in 70% ethanol.

The scientists prepared the continuous (fluid) phase by mixing 2% of soy lecithin with tributyrin, a triglyceride. They tested three combinations of flow rates. Rhodamine B, a tracer dye, was used as a model core material to evaluate the release properties.

The scientists found that by using release half-life (t50) as an indicator, a wide range of release rates, ranging from three minutes to 62 minutes, could be achieved, by simply adjusting the zein concentration in the dispersed phase, and the continuous and dispersed phase flow rates.

The release rate of the encapsulated Rhodamine B was positively correlated with the zein concentration and the flow rate of the dispersed phase.

Further information. Youngsoo Lee, Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 382K Agricultural Engineering Sciences Building, 1304 W. Pennsylvania, Urbana, IL 61801; phone: 217-333-9335; email:

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Author:Lee, Youngsoo
Publication:Emerging Food R&D Report
Date:Feb 1, 2019
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